High-performance light-assisted lithium-oxygen battery cathode material, and preparation method and application thereof

Abstract

The application relates to the technical field of lithium-oxygen batteries, in particular to a high-performance light-assisted lithium-oxygen battery positive electrode material and a preparation method and application thereof. The positive electrode material is obtained by compounding Fe2O3 with photocatalytic performance and FeNi2Se4 with a spinel structure. Fe2O3 is introduced to perform surface modification on the spinel structure FeNi2Se4 material, more light can be absorbed, and the decomposition efficiency of the photo-generated electron-hole pairs in the FeNi2Se4 is accelerated, the prepared positive electrode material FeNi2Se4@Fe2O3 has high light utilization, the light absorption and electron transmission efficiency of the positive electrode material are improved, more visible light can be captured by the positive electrode material, the positive electrode material has excellent catalytic performance in the lithium-oxygen battery, and the battery performance can be obviously improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-oxygen battery technology, specifically to a high-performance photo-assisted lithium-oxygen battery cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-oxygen batteries (Li-O2 or Li-air batteries) are a high-energy-density battery technology. They use lithium metal and oxygen as the positive and negative electrode materials, releasing energy through a redox reaction. In a lithium-oxygen battery, lithium metal acts as the negative electrode, and oxygen (usually from the air) acts as the positive electrode. When the battery operates, lithium metal oxidizes to form lithium ions (Li₂O₂ or Li₂O₂). + Oxygen will be reduced to form oxide ions (O2). - These ions move in the electrolyte, which then transfers them between the positive and negative electrodes, thus completing the charging and discharging process of the battery.

[0003] Compared to currently available commercial lithium-ion batteries, lithium-oxygen batteries have a higher theoretical energy density (11680 Wh / kg). -1 Li-O2 is expected to become a high-energy, low-cost, and pollution-free commercial power battery of the future. However, its poor actual capacity and slow conversion rate severely limit its practical application. The charging and discharging process of lithium-oxygen batteries is actually the formation and decomposition of lithium peroxide. As charging and discharging proceeds, the slow lithium peroxide conversion rate leads to the accumulation of a large amount of discharge products on the cathode, preventing oxygen from entering, causing the battery capacity to decrease or even become unusable.

[0004] Currently, lithium-oxygen batteries are still in the research and development stage, requiring further improvement and optimization for reliable commercial applications. To address some of the challenges faced by lithium-oxygen batteries in practical applications, using catalysts on the positive electrode to improve battery performance is an effective method. Spinel-structured oxides typically exhibit good performance. <HighlyStable Spinel Oxide Cathode for Rechargeable Li-O2 Batteries in Non-Aqueous Liquid and Gel-Based Electrolytes> Bimetallic spinel oxide NiFe2O4 was synthesized as a cathode catalyst, which improved the battery's discharge capacity. However, the reduction in overpotential was not significant, and the influence of light conditions on catalytic performance was not considered. How to prepare high-performance photoelectric cathodes to improve the electrochemical performance of light-assisted lithium-air batteries has become a pressing technical problem in this field. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of poor photocatalytic performance and poor battery capacity of existing lithium-oxygen battery cathode materials, and provides a high-performance photo-assisted lithium-oxygen battery cathode material and its preparation method, and applies it to high-performance photo-assisted lithium-oxygen batteries to overcome the above-mentioned defects.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a high-performance photo-assisted lithium-oxygen battery cathode material, wherein the cathode material is obtained by combining Fe2O3 with photocatalytic properties and FeNi2Se4 with a spinel structure.

[0007] This invention proposes a high-performance photo-assisted lithium-oxygen battery cathode material, FeNi2Se4@Fe2O3, obtained by combining photocatalytically active Fe2O3 with spinel-structured FeNi2Se4. This FeNi2Se4@Fe2O3 material is petal-shaped, composed of single-crystal Fe2O3 and polycrystalline FeNi2Se4, exhibiting a unique morphology and structure that provides a large specific surface area and exposes more active sites. Selenides generally exhibit better catalytic performance than their oxides. FeNi2Se4 selenide is a typical spinel-structured semiconductor with excellent electronic structure; however, its poor light-harvesting ability hinders its photocatalytic performance. By combining photocatalytically active Fe2O3 with FeNi2Se4, the resulting FeNi2Se4@Fe2O3 material significantly enhances the light-harvesting ability of the cathode material and substantially increases the battery capacity compared to the original FeNi2Se4 material.

[0008] The cathode material FeNi2Se4@Fe2O3 proposed in this invention has the following advantages: First, the large specific surface area of ​​the flower-like FeNi2Se4@Fe2O3 material provides more active surface sites, increasing the contact area between the catalyst and oxygen, thereby improving reaction efficiency. Second, by introducing Fe2O3 to modify the surface of the spinel-structured FeNi2Se4 material, the number of active sites and surface reactivity are increased. Surface modification helps improve light absorption and electron transport efficiency, allowing the material to capture more visible light. This visible light will excite photogenerated electrons and holes on the material. During discharge, photogenerated electrons and holes promote the formation of lithium peroxide, and during charging, they promote the decomposition of lithium peroxide, thereby improving photocatalytic activity.

[0009] The overpotential of FeNi2Se4 as the positive electrode is 0.6V under illumination and 0.91V in darkness, while the overpotential of FeNi2Se4@Fe2O3 as the positive electrode is only 0.1V under illumination. The significantly lower overpotential of FeNi2Se4 demonstrates that the introduction of Fe2O3 effectively helps absorb more light and accelerates the decomposition efficiency of photogenerated electron-hole pairs in FeNi2Se4, thus significantly reducing the overpotential. Lowering the overpotential allows the battery to more efficiently convert electrical energy into chemical energy and release it when needed. This helps improve battery energy efficiency, extend battery life, and enhance overall performance. Simultaneously, a lower overpotential reduces the rate of electrochemical reactions within the battery, thereby slowing down the aging process.

[0010] In summary, the FeNi2Se4@Fe2O3 cathode material prepared by this invention exhibits high light utilization. The introduction of Fe2O3 to modify the surface of the spinel-structured FeNi2Se4 material improves light absorption and electron transport efficiency, allowing the material to capture more visible light. Therefore, under illumination conditions, using the cathode catalyst provided by this invention can improve battery reaction kinetics, reduce energy loss, and enhance battery discharge performance and cycle stability. Furthermore, in terms of lithium-oxygen battery performance, FeNi2Se4@Fe2O3 as the cathode electrode exhibits the highest discharge current density of 2.59 mA / cm². 2 It has a minimum charging initiation potential of 3.33V and an overpotential of 0.1V. The full cell specific capacity is 13240mAh / g, and the discharge current density under illumination using FeNi2Se4 material as the positive electrode is 1.13mA / cm². 2 The charging initiation potential is 3.52V, and the overpotential is 0.6V. The full cell specific capacity is 7069mAh / g. This indicates that the FeNi2Se4@Fe2O3 material prepared by surface modification of spinel structure FeNi2Se4 material by introducing Fe2O3 has excellent catalytic performance in lithium oxygen battery and can significantly improve battery performance.

[0011] Secondly, the present invention provides a method for preparing the aforementioned high-performance photo-assisted lithium-oxygen battery cathode material, comprising the following steps: S1 disperses FeCl2 and NiCl2 in an alkaline aqueous solution, then transfers them to a reaction vessel for hydrothermal reaction. After the reaction is completed, the mixture is separated, purified, and dried to obtain FeNi double hydroxide powder. S2. Place the Se powder upstream of the gas flow direction, and place the FeNi double hydroxide powder obtained in step S1 downstream of the gas flow direction. After heating and sintering in an inert gas environment, FeNi2Se4 powder is obtained. S3. Potassium ferricyanide is dispersed in an alkaline aqueous solution, and the FeNi2Se4 powder obtained in step S2 is added to it. After stirring, the precipitate is collected to obtain a precursor. The precursor is then calcined in air to obtain FeNi2Se4@Fe2O3, which is the cathode material.

[0012] Preferably, the inert gas environment is argon.

[0013] Preferably, the molar ratio of FeCl2 to NiCl2 is 1:1 to 1:2.

[0014] The morphology of FeNi double hydroxide can be controlled by adjusting the ratio of FeCl2 to NiCl2. When the molar ratio of FeCl2 to NiCl2 is 1:1 to 1:2, the desired crystal structure and morphology can be achieved.

[0015] Preferably, the pH of the alkaline aqueous solution is 12 to 14.

[0016] A pH value below 12 hinders the hydrolysis of metal ions and the formation of hydroxides. This can slow down the reaction rate and limit product formation. Furthermore, it may cause other reactions of the metal ions, such as precipitation or oxidation, thus affecting the formation of the desired product. A pH value above 14 leads to unstable product morphology or undesirable results, and may also cause excessive hydrolysis of metal ions. In addition, excessively high pH values ​​may trigger side reactions or reduce the reaction rate. After numerous experiments, it was found that controlling the pH of the alkaline aqueous solution to 12–14 in this invention provides suitable reaction conditions, promotes the hydrolysis of metal ions, and facilitates the formation of the desired product, resulting in the best product quality.

[0017] Preferably, the temperature of the hydrothermal reaction in step S1 is 160–200°C, and the heating time is 8–16 h.

[0018] Preferably, the heating and sintering temperature in step S2 is 400–800°C, and the heating time is 2–4 hours.

[0019] Preferably, the firing temperature in step S3 is 100-130°C and the heating time is 3-5 hours.

[0020] The above preparation process controls the hydrothermal reaction, heating and sintering, and the temperature and time of the firing, which directly affects the photocatalytic performance and battery capacity of the final cathode material FeNi2Se4@Fe2O3. Among them, the heating and sintering temperature has the greatest impact on the cathode material FeNi2Se4@Fe2O3. When the heating and sintering temperature is 600℃, the FeNi2Se4 prepared and used to synthesize the cathode material FeNi2Se4@Fe2O3 results in a battery with the lowest overpotential of 0.1V and the highest full-cell specific capacity of 13240mAh / g.

[0021] Thirdly, the present invention provides a high-performance photo-assisted lithium-oxygen battery cathode sheet, comprising a substrate and the cathode material coated on the substrate or the cathode material prepared by the method thereof.

[0022] As preferred options, conductive carbon black, polyvinylidene fluoride, and N-methylpyrrolidone are also included.

[0023] Conductive carbon black: Conductive carbon black is a material with excellent electrical conductivity. Adding conductive carbon black can increase the conductivity of electrodes. With its high surface area and conductivity, conductive carbon black provides more electron channels, promoting charge transfer and ion transport. This helps to improve the electrode's conductivity and reaction rate, thereby enhancing the electrode's catalytic performance.

[0024] Polyvinylidene fluoride (PVDF): PVDF is a commonly used electrode adhesive. Adding PVDF to the slurry helps to bond and cure electrode materials. PVDF has good adhesion and chemical stability, and can firmly bond materials such as catalysts and conductive carbon black together to form the electrode structure. In addition, PVDF also has a certain degree of hydrophobicity, which can improve the durability and stability of the electrode.

[0025] N-Methylpyrrolidone (NMP): As an organic solvent, NMP has good solubility and volatility. Adding NMP to the slurry can uniformly disperse the components and provide suitable viscosity and flowability, making the slurry easy to coat onto carbon paper or other substrates. During the preparation process, NMP evaporates, leaving a uniformly dispersed material layer.

[0026] In summary, conductive carbon black provides the electrode with electrical conductivity, PVDF acts as a binder to cure and bond the electrode material, and NMP acts as an organic solvent to ensure uniform dispersion of the slurry and facilitate coating. The addition and synergistic effects of these components result in electrode sheets with excellent conductivity, adhesion, and fabrication properties.

[0027] Fourthly, the present invention provides the application of the aforementioned positive electrode material, the aforementioned positive electrode sheet, or the positive electrode material prepared by the method in high-performance photo-assisted lithium-oxygen batteries.

[0028] The present invention has the following beneficial effects: (1) In this invention, Fe2O3 is introduced to modify the surface of spinel structure FeNi2Se4 material. The resulting cathode material FeNi2Se4@Fe2O3 has high light utilization rate, which improves the light absorption and electron transport efficiency of the cathode material, enabling the cathode material to capture more visible light. It has excellent catalytic performance in lithium-oxygen batteries and can significantly improve battery performance. (2) The positive electrode material FeNi2Se4@Fe2O3 proposed in this invention is petal-shaped and is composed of single-crystal Fe2O3 and polycrystalline FeNi2Se4. It is a material with special morphology and structure, which can provide a large specific surface area and expose more active sites, increase the contact area between the catalyst and oxygen, and thus improve the battery reaction efficiency. (3) By introducing Fe2O3 to modify the surface of spinel-structured FeNi2Se4 material, more light can be absorbed, accelerating the decomposition efficiency of photogenerated electron-hole pairs in FeNi2Se4, thereby significantly reducing the overpotential. Lowering the overpotential allows the battery to more efficiently convert electrical energy into chemical energy and release it when needed. This helps improve the battery's energy efficiency, extend its lifespan, and enhance overall performance. Simultaneously, a lower overpotential reduces the electrochemical reaction rate within the battery, thus slowing down the aging process. Attached Figure Description

[0029] Figure 1 The diagram shows the traditional AB2O4 spinel structure and the elemental distribution and valence states of the FeNi2Se4 synthesized in this invention.

[0030] Figure 2 The X-ray diffraction (XRD) patterns are of the materials prepared in Examples 1, 2, 3 and Comparative Example 1 of this invention.

[0031] Figure 3 This is a transmission electron microscope image of the positive electrode material FeNi2Se4@Fe2O3 prepared in Example 1 of the present invention.

[0032] Figure 4 The CV test curves of the cathode materials prepared in Examples 1, 2, 3 and Comparative Example 1 of this invention are used in lithium-oxygen batteries.

[0033] Figure 5 The first charge-discharge curves of the cathode materials prepared in Examples 1, 2, 3 and Comparative Example 1 of this invention are shown in the lithium-oxygen battery.

[0034] Figure 6The full-cell capacity distribution of the cathode materials prepared in Examples 1, 2, 3 and Comparative Example 1 of this invention when applied in lithium-oxygen batteries. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0036] A schematic diagram of the traditional AB₂O₄ spinel structure and the elemental distribution and valence states of the FeNi₂Se₄ synthesized in this invention are shown in the schematic diagram. Figure 1 As shown.

[0037]

Example

[0038] Example 2 The difference between this embodiment and Embodiment 1 is that the high-temperature sintering temperature in step 2 is 600℃, while the rest is basically the same as in Embodiment 1. The positive electrode sheet prepared in this embodiment is named FeNi2Se4@Fe2O3-600.

[0039] Example 3 The difference between this embodiment and embodiment 1 is that the high-temperature sintering temperature in step 2 is 800℃, while the rest is basically the same as in embodiment 1. The positive electrode sheet prepared in this embodiment is named FeNi2Se4@Fe2O3-800.

[0040] Example 4 The difference between this embodiment and Embodiment 1 is that the amount of NiCl2 added in step 1 is 0.25 mol, while the rest is basically the same as in Embodiment 1.

[0041] Example 5 The difference between this embodiment and Embodiment 1 is that the amount of NiCl2 added in step 1 is 0.4 mol, while the rest is basically the same as in Embodiment 1.

[0042] Example 6 The difference between this embodiment and Embodiment 1 is that the hydrothermal reaction temperature in step 1 is 160°C and the time is 16 hours, while the rest is basically the same as in Embodiment 1.

[0043] Example 7 The difference between this embodiment and Embodiment 1 is that the hydrothermal reaction temperature in step 1 is 200°C and the time is 8 hours, while the rest is basically the same as Embodiment 1.

[0044] Example 8 The difference between this embodiment and embodiment 1 is that the firing temperature in step 3 is 100°C and the time is 4 hours, while the rest is basically the same as in embodiment 1.

[0045] Example 9 The difference between this embodiment and embodiment 1 is that the firing temperature in step 3 is 130°C and the time is 3 hours, while the rest is basically the same as in embodiment 1.

[0046] Comparative Example 1 S1: FeNi double hydroxide was prepared by a hydrothermal method. 50 mL of deionized water was added to a beaker, along with 0.25 mol FeCl2, 0.5 mol NiCl2, and 0.005 mol NaOH (to create an alkaline environment, pH around 13). The mixture was stirred until homogeneous, then transferred to a 100 mL hydrothermal reactor and maintained at 180 °C for 12 h. After the reaction, the FeNi double hydroxide powder was centrifuged, washed, and dried overnight at 60 °C in a vacuum drying oven. S2: FeNi2Se4 was prepared by high-temperature sintering. Excess Se powder was placed in a ceramic boat and placed upstream of a tube furnace. 0.2g of FeNi double hydroxide powder from step 1 was placed in a second ceramic boat and placed downstream of the tube furnace. FeNi2Se4 powder was obtained by sintering at 400℃ for 2 hours under argon atmosphere. S3: Mix the FeNi2Se4 powder from step S2 with conductive carbon black and PVDF in a mass ratio of 8:1:1. Add an appropriate amount of NMP to make a uniform slurry. Coat the slurry onto carbon paper with a scraper and place it in a vacuum drying oven at 90°C for 12 hours. Cut it into round pieces with a diameter of 14 mm to obtain the positive electrode sheet. The positive electrode sheet prepared in this embodiment is named FeNi2Se4.

[0047] [Performance Testing] Electrolyte and separator: 1M LiTFSI@tetraethylene glycol dimethyl ether (TEGDME) is used as the electrolyte, and Whatman W / D glass fiber membrane (25mm thick) is used as the separator.

[0048] Battery assembly: The FeNi2Se4@Fe2O3-400, FeNi2Se4@Fe2O3-600, and FeNi2Se4@Fe2O3-800 prepared in the experimental example, and the FeNi2Se4 prepared in Comparative Example 1, were used as positive electrodes. The batteries were assembled in the following order: negative electrode shell, lithium sheet, separator, electrolyte, positive electrode shell, gasket, and positive electrode shell. The batteries were then compacted using a button cell sealing machine to obtain Li-O2 batteries. Light-assisted testing was provided by a xenon lamp with a color temperature of 3000K-5000K. Charge-discharge tests were conducted in an oxygen glove box. The test results are as follows: Figure 2 (a) X-ray diffraction (XRD) patterns of the materials prepared in Examples 1, 2, 3 and Comparative Example 1 of the present invention; Figure 2 (b) is a magnified view at the 34-36° position. (Through...) Figure 2 It can be seen that: comparing the XRD images of FeNi2Se4@Fe2O3 synthesized in Examples 1, 2, and 3 with Fe2O3-PDF#86-0550, the characteristic peaks at 24° and 63° belong to Fe2O3; through Figure 2(b) It can be seen that, relative to FeNi2Se4, the characteristic peak at 35° gradually shifts to the left as the reaction temperature increases, which indicates that the increase in reaction temperature will affect the structure of FeNi2Se4@Fe2O3.

[0049] Figure 3 (a) is a TEM image of FeNi2Se4@Fe2O3 prepared in Example 1 of the present invention; Figure 3 (b) is the corresponding HR-TEM image; Figure 3 (c)-3(d) are the Fourier transforms of the boundary lines on both sides of the HR-TEM image. Figure 3 (a) It can be seen that the FeNi2Se4@Fe2O3-600 synthesized in Experimental Example 1 is petal-shaped, and its unique morphology provides a large specific surface area and exposes more active sites. Figure 3 In (b), a boundary can be clearly seen, which is the interface formed by the composite of FeNi2Se4 and Fe2O3. The lattice spacing of 0.23 nm is typical of the (104) crystal plane of Fe2O3, and 0.27 nm is the (002) crystal plane of FeNi2Se4. Figure 3 In (c)-3(d), it was verified that the two regions with separated boundaries belong to single-crystal Fe2O3 and polycrystalline FeNi2Se4, respectively.

[0050] Figure 4 Table 1 shows the CV test curves of the cathode materials prepared in Examples 1, 2, 3, and Comparative Example 1 of this invention when applied to lithium-oxygen batteries. Figure 4 The discharge current density and charging initiation potential of different batteries were measured. The scan rate was 0.1 mV, and the voltage range was 2.1-4.5 V. Figure 4 The embedded image is a magnified view of a portion of the initial discharge voltage peak. Figure 4 It can be seen that the discharge current density of FeNi2Se4@Fe2O3 under illumination conditions exceeds that of FeNi2Se4 in both illuminated and dark environments, and FeNi2Se4@Fe2O3-600 exhibits the highest discharge current density of 2.59 mA / cm² under illumination conditions. 2 (FeNi2Se4 dark is 0.97mA / cm) 2 The FeNi2Se4 light intensity is 1.13 mA / cm². 2 The light intensity of FeNi2Se4@Fe2O3-400 is 1.28 mA / cm². 2 FeNi2Se4@Fe2O3-800 light has an amplitude of 2.25 mA / cm². 2The lower charging onset potential of 3.33V (3.44V for FeNi2Se4 dark, 3.52V for FeNi2Se4 light, 3.43V for FeNi2Se4@Fe2O3-400 light, and 3.34V for FeNi2Se4@Fe2O3-800 light) indicates that the photocatalytic performance of the material is improved after Fe2O3 is added, and FeNi2Se4@Fe2O3 synthesized at 600℃ has the best battery performance.

[0051] Table 1 Figure 4 Discharge current density and charging start potential of different batteries

[0052] Figure 5 The first charge-discharge curves of the cathode materials prepared in Examples 1, 2, 3, and Comparative Example 1 of this invention are shown in the lithium-oxygen battery; the charge-discharge current density is 0.1C. Figure 5 It can be seen that the prepared FeNi2Se4@Fe2O3-600 light battery has the smallest overpotential of 0.1V (0.91V for FeNi2Se4 dark, 0.6V for FeNi2Se4 light, 0.31V for FeNi2Se4@Fe2O3-400 light, and 0.53V for FeNi2Se4@Fe2O3-800 light). This indicates that FeNi2Se4 prepared by high-temperature sintering at 600℃ has the best lithium peroxide decomposition ability when used to synthesize FeNi2Se4@Fe2O3.

[0053] Figure 6 The full-cell capacity distribution of the cathode materials prepared in Examples 1, 2, 3, and Comparative Example 1 of this invention is shown in the diagram. The test environment was a pure oxygen glove box with a current density of 0.1C. Figure 6 It can be seen that FeNi2Se4@Fe2O3-600 light has the highest full-cell specific capacity of 13240mAh / g.

[0054] In summary, the FeNi2Se4@Fe2O3 cathode material provided by this invention has a petal-like structure, composed of single-crystal Fe2O3 and polycrystalline FeNi2Se4, which can provide a large specific surface area and expose more active sites. In terms of lithium-oxygen battery performance, FeNi2Se4@Fe2O3-600 exhibits the highest discharge current density of 2.59 mA / cm². 2The lowest charging initiation potential is 3.33V; and its overpotential is 0.1V. The full cell specific capacity is 13240mAh / g, which indicates that: (1) FeNi2Se4@Fe2O3 material has excellent catalytic performance in lithium oxygen battery and can significantly improve battery performance; (2) FeNi2Se4 prepared by high temperature sintering at 600℃ has better performance when used to synthesize FeNi2Se4@Fe2O3-600.

Claims

1. A high-performance photo-assisted lithium-oxygen battery cathode material, characterized in that, The cathode material is obtained by combining Fe2O3 with photocatalytic properties with FeNi2Se4 with a spinel structure.

2. A method for preparing the high-performance photo-assisted lithium-oxygen battery cathode material as described in claim 1, characterized in that, Includes the following steps: S1 disperses FeCl2 and NiCl2 in an alkaline aqueous solution, then transfers them to a reaction vessel for hydrothermal reaction. After the reaction is completed, the mixture is separated, purified, and dried to obtain FeNi double hydroxide powder. S2. Place the Se powder upstream of the gas flow direction, and place the FeNi double hydroxide powder obtained in step S1 downstream of the gas flow direction. After heating and sintering in an inert gas environment, FeNi2Se4 powder is obtained. S3. Potassium ferricyanide is dispersed in an alkaline aqueous solution, and the FeNi2Se4 powder obtained in step S2 is added to it. After stirring, the precipitate is collected to obtain a precursor. The precursor is then calcined in air to obtain FeNi2Se4@Fe2O3, which is the cathode material.

3. The method as described in claim 2, characterized in that, The molar ratio of FeCl2 to NiCl2 is 1:1 to 1:

2.

4. The method as described in claim 2 or 3, characterized in that, The pH of the alkaline aqueous solution is 12 to 14.

5. The method as described in claim 2, characterized in that, The hydrothermal reaction temperature in step S1 is 160–200°C, and the heating time is 8–16 hours.

6. The method as described in claim 5, characterized in that, In step S2, the heating and sintering temperature is 400–800℃, and the heating time is 2–4 hours.

7. The method as described in claim 5 or 6, characterized in that, In step S3, the firing temperature is 100-130℃ and the heating time is 3-5 hours.

8. A high-performance photo-assisted lithium-oxygen battery positive electrode, characterized in that, It includes a substrate and a positive electrode material as described in claim 1 coated on the substrate, or a positive electrode material prepared by the method described in any one of claims 2 to 7.

9. The high-performance photo-assisted lithium-oxygen battery positive electrode sheet as described in claim 8, characterized in that, It also includes conductive carbon black, polyvinylidene fluoride, and N-methylpyrrolidone.

10. The application of the cathode material of claim 1, or the cathode material prepared by the method of any one of claims 2 to 7, or the cathode sheet of claim 8 or 9, in a high-performance photo-assisted lithium-oxygen battery.

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